The present invention relates to the formation of biofilms, more particularly the present invention provides apparatuses for forming biofilms on various surfaces as well as methods for testing the effects of antimicrobial agents on the formation of biofilms.
Extensive study into the growth properties of bacteria in recent years has shown that bacteria form complex layers that adhere to surfaces. These complex forms of bacteria are known as biofilms, or sessile bacteria. Biofilms may cause problems in a variety of areas including the bodies of humans and animals, food processing, health care facilities and many other industries.
It is now known widely that bacteria in the form of biofilms are more resistant to antimicrobial reagents than planktonic bacteria. Yet traditional testing of antimicrobial reagents is performed utilizing planktonic bacterial. Thus, bacterial inhibitory concentration of antimicrobial reagent may be underestimated, with the result that the wrong antimicrobial reagent or wrong amount of antimicrobial reagent may be used for the treatment of bacteria.
One type of device for monitoring biofilm buildup is described in the Canadian Journal of Microbiology (1981), Volume 27, pages 910-927, in which McCoy et al. describes the use of a so-called Robins device. The Robins device includes a tube through which water in a recycling circuit can flow. The tube has a plurality of ports within the tube wall, each port being provided with a removable stud, the stud having a biofoulable surface and being capable of being retained within the port in a fixed relationship with respect to the tube so that the biofoulable surface forms part of the internal surface of the tube. Each of the studs may be removed from the ports after a desired time interval and the surfaces analyzed for the growth of microorganisms. Alternatively, any surface growth may be removed and studied independent of the stud. The number of microorganism can be estimated for instance by physical or chemical means, e.g. by detection of bacterial ATP or by further culturing the microorganisms and analyzing the products.
Referring now to U.S. Pat. No. 5,349,874, Schapira, et al. there is shown another device for biofilm growth. Bacterial growth is determined in a water carry conduit by providing a plurality of removable studs disposed within the conduit, or in a second conduit parallel to the first. The studs may be removed for analysis of biofilm growth on the studs. Such devices that utilize removable studs in a single conduit result in rather lengthy processing times and do not provide for rapid response times for testing of several different antimicrobial reagents.
In still another device which is described in Simple Method for Measuring the Antibiotic Concentration Required to Kill Adherent Bacteria, Miyake et al., Chemotherapy 1992; 38, 286-290, staphylococcus aureus cells adhered to the bottom of a 96 well plastic tissue culture plate were treated with serially diluted antibiotic solutions, viability of the cells were judged by their growth after a further 24 hours incubation. This method has the disadvantage of inconsistent colonization of sessile bacteria and settling of planktonic bacteria.
It would be desirable to provide an apparatus and method for testing the effects of materials, such as surface coatings, on biofilm growth. In addition, it would be desirable to provide an apparatus and method for testing the effects of materials on biofilm growth which provides rapid response times and the ability to test multiple materials or antimicrobial reagents at once.
In one aspect of the invention, there is provided a method for growing a plurality of biofilms. The method includes proving a plurality of biofilm adherent sites, the biofilm adherent sites further including a surface material, wherein the surface material models a surface likely to be involved in biofilm formation. A liquid growth medium is arranged to flow across the biofilm adherent sites, and bacteria is incubated in the presence of the liquid growth medium.
In another aspect of the invention, there is provided a method for testing biofilm growth on surface coatings in a controlled environment. The method includes, providing a plurality of biofilm adherent sites, coating the biofilm adherent sites with a material which acts as a model for a surface likely to be involved in biofilm formation, providing a liquid growth medium arranged to flow across the biofilm adherent sites, agitating the liquid growth medium to flow across the biofilm adherent sites and growing bacteria on the biofilm adherent sites.
In another aspect of the present invention, there is provided an apparatus for testing the growth of biofilms. The apparatus includes a first body having first and second surfaces, a second body having sides and a bottom defining a vessel, the second body adapted to receive the first body. The first body further including projections extending from the first surface, wherein the projections are adapted to receive a material for biofilm growth. The vessel further capable of receiving fluid in a plurality of depressions and including a means to flow the liquid within the vessel about the members.
In yet another aspect of the present invention, there is provided a method for testing the formation of biofilm growth on a material or surface coating. The method includes partially covering a plurality of projections in a testing apparatus with a material to be tested for biofilm formation. Placing the projections into a first vessel containing at least one well, wherein the well includes a liquid growth medium and a biofilm forming organism, and removing the projections from the first vessel and placing the projections into a second vessel, wherein the second vessel contains a second medium.